fix(plugin-essentials): fix hash validation pattern of explain peer-requirements

[pudovmaxim]

What's the problem this PR addresses?

This fix of issue described here #6880

How did you fix it?

Fix validation of hash at explain peer-requirements command

Checklist

• I have read the Contributing Guide.

• I have set the packages that need to be released for my changes to be effective.

• I will check that all automated PR checks pass before the PR gets reviewed.

[droddy]

Do we know that all peer dependency hashes will be exactly 6 characters after 'p' now?
Is this likely to break again if/when the length of that particular has changes again?

[sekyungk]

I am the author of #6829. I didn't catch this issue. Since yarn explain is unusable, I hope it can be fixed quickly. Let me mention @arcanis , who is the reviewer of #6829. Thank you.